Manganese-Driven Carbon Oxidation at Oxic–Anoxic Interfaces

Jones, Morris; Nico, Peter; Ying, Samantha C.; Regier, Tom; Thieme, Jürgen; Keiluweit, Marco

doi:10.1021/acs.est.8b03791

Cited by 62 publications

(85 citation statements)

References 47 publications

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“…) environments and also at oxic‐anoxic interfaces (Jones et al . ). Nitrates are strong oxidants under both acidic and alkaline conditions (Quin et al .…”

Section: Discussionmentioning

confidence: 97%

Taphonomic experiments resolve controls on the preservation of melanosomes and keratinous tissues in feathers

et al. 2019

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Fossils are a key source of data on the evolution of feather structure and function through deep time, but their ability to resolve macroevolutionary questions is compromised by an incomplete understanding of their taphonomy. Critically, the relative preservation potential of two key feather components, melanosomes and keratinous tissue, is not fully resolved. Recent studies suggesting that melanosomes are preferentially preserved conflict with observations that melanosomes preserve in fossil feathers as external moulds in an organic matrix. To date, there is no model to explain the latter mode of melanosome preservation. We addressed these issues by degrading feathers in systematic taphonomic experiments incorporating decay, maturation and oxidation in isolation and combination. Our results reveal that the production of mouldic melanosomes requires interactions with an oxidant and is most likely to occur prior to substantial maturation. This constrains the taphonomic conditions under which melanosomes are likely to be fossilized. Critically, our experiments also confirm that keratinous feather structures have a higher preservation potential than melanosomes under a range of diagenetic conditions, supporting hitherto controversial hypotheses that fossil feathers can retain degraded keratinous structures.

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“…) environments and also at oxic‐anoxic interfaces (Jones et al . ). Nitrates are strong oxidants under both acidic and alkaline conditions (Quin et al .…”

Section: Discussionmentioning

confidence: 97%

Taphonomic experiments resolve controls on the preservation of melanosomes and keratinous tissues in feathers

et al. 2019

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“…In addition to Fe and Al, redox transformations of Mn may influence SOC mobilization (Jones et al, 2018). While reactive Mn decreased with increasing saturation frequency, the explanatory power of all Mn variables (total and extractable) for prediction of total C was low (Table 1), suggesting that Mn did not influence C accumulation to the same extent as Fe and Al.…”

Section: Contrasting Mineral-organic Interactions Across Variable Saturation Frequency Soilsmentioning

confidence: 99%

Organo-mineral interactions and soil carbon mineralizability with variable saturation cycle frequency

et al. 2020

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The response of mineral-stabilized soil organic carbon (SOC) to environmental change is a source of uncertainty in the understanding of SOC cycling. Fluctuating wet-dry cycles and associated redox changes in otherwise welldrained soils may drive mineral dissolution, organic carbon (OC) mobilization, and subsequent OC mineralization. However, the extent to which rapid fluctuations between water-saturated and unsaturated conditions (i.e., flashy conditions) result in long-term changes in mineral composition and organo-mineral interactions is not well understood. In this study, the effect of variable saturation frequency on soil mineral composition, mineral-associated OC, and OC mineralizability was tested using selective dissolution, bulk spectroscopy, microscale imaging, and aerobic-anaerobic incubation experiments. Previous water table fluctuation measurements and diagnostic profile characteristics at Hubbard Brook Experimental Forest (NH) were used to identify soils with high, medium, and low saturation frequency regimes (defined by historical water table cycling frequency; i.e., water table presence and recession in the upper B horizon). We found the amount of OC released during extractions targeting non-crystalline minerals was of similar magnitude as extracted iron (Fe) in lower saturation frequency soils. However, the magnitude of extracted OC was 2.5 times greater than Fe but more similar to extractable aluminum (Al) in higher saturation frequency soils. Bulk soil Fe was spatially more strongly correlated to soil organic matter (SOM) in lower saturation frequency soils (Spearman Rank r s = 0.62, p < 0.005), whereas strong correlations between Al and SOM were observed in higher saturation frequency soils (r s = 0.88, p < 0.005) using nanoscale secondary ion mass spectrometry (NanoSIMS) imaging. Characterization of bulk soil Fe with X-ray absorption spectroscopy showed 1.2-fold greater Fe(II) and 1-fold lower contribution of Feorganic bonding in soils with high saturation frequency. Fe(III) interactions with carboxylic and aromatic C were identified with 13 C nuclear magnetic resonance (NMR) spectroscopy Fe(III) interference experiments. Additionally, carboxylic acid enrichment in high saturation frequency soils quantified by C K-edge X-ray absorption spectroscopy point towards the role of carboxylic functional groups in Al-organic in addition to Feorganic interactions. In our incubation experiments, a doubling in short-term CO 2 evolution (per unit total soil C) was detected for high relative to low saturation frequency soils. Further, an order of magnitude increase in CO 2 evolution (per unit water-extractable OC) following anaerobic incubation was only detected in high saturation frequency soils. The observed shift towards Al-dominated SOC interactions and higher OC mineralizability highlights the need to describe C stabilization in soils with flashy wet-dry cycling separately from soils with low saturation frequency or persistent saturation.

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“…The relatively high proportion of particulate Hg vastly decreased during the draining period (Fig. 3b,c) and we speculate that this change is a result of the mobilization of the POM-Hg pool by mineralization/degradation of NOM which sorbed Hg during the draining period (Jones et al, 2018). In summary, flooding of the pasture field soils did mobilize only a small pool of particulate bound Hg which was exhausted within the first flooding period.…”

Section: Mercury Release and Sequestrationmentioning

confidence: 73%

“…shown to enhance microbial respiration and therefore NOM degradation (Sunda and Kieber, 1994). Further, Mn oxidation was shown to enhance the degradation of larger NOM to LMW-NOM (Jones et al, 2018). Thus, we interpret the second Hg release in Rep 3 as a degradation/mineralization of NOM that bound Hg.…”

Section: Mercury Release and Sequestrationmentioning

confidence: 77%

“…Methylation hotspots (redox boundaries) are also places of NOM degradation and mineralization. The degradation of large NOM to more bioavailable low molecular weight (LMW) compounds promoted by microbial Mn oxidation, especially in systems with neutral pH (Jones et al, 2018;Sunda and Kieber, 1994;Ma et al, 2020), is also hypothesized to increase bioavailability of Hg-NOM. However, amendments of Mn oxides were also shown to inhibit Fe, SO4reducing conditions and thus MeHg formation in sediments (Vlassopoulos et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

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Comment on bg-2020-466

Poulin¹

2021

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Floodplain soils polluted with high levels of mercury (Hg) are potential point sources to downstream eco-systems.Repeated flooding (e.g. redox cycling) and agricultural activities (e.g. organic matter addition) may influence the fate and speciation of Hg in these soil systems. The formation and aggregation of colloids and particles influences both Hg mobility and its bioavailability to methylmercury (MeHg) forming microbes. In this study, we conducted a microcosm flooding-draining experiment on Hg polluted floodplain soils originating from an agriculturally used area situated in the Rhone Valley (Valais, Switzerland). The experiment comprised two 14 days flooding periods separated by one 14 days draining period. The effect of freshly added natural organic matter on Hg dynamics was assessed by adding liquid cow manure (+MNR) to two control soils characterized by different Hg (47.3 ± 0.6 mg kg -1 or 2.38 ± 0.01 mg kg -1 ) and organic carbon (OC: 1.92 wt. % or 3.45 wt. %) contents. During the experiment, the release, colloid formation and methylation of Hg in the soil solution were monitored. Upon manure addition in the highly polluted soil (lowest OC), an accelerated release of Hg to the soil solution could be linked to a fast reductive dissolution of Mn oxides. The manure treatments showed a fast sequestration of Hg and a higher percentage of particulate (0.02 -10 µm) bound Hg. As well, analyses of soil solutions by asymmetrical flow field-flow fractionation coupled with inductively coupled plasma mass spectrometry (AF4-ICP-MS) revealed a proportional increase of colloidal DOM-Hg and inorganic colloidal Hg (+MNR: 70 -100 %; control: 32 -70 %) upon manure addition. Our experiment shows that net Hg methylation (MeHg/Hg) was highest after the first draining period and decreased again after the second flooding period. No significant effects on methylation upon manure addition was found. The results of this study suggest that manure addition may promote sequestration by Hg complexation on large organic matter components and the formation/aggregation of inorganic HgS(s) colloids in Hg polluted fluvisols with low levels of natural organic matter.

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Manganese-Driven Carbon Oxidation at Oxic–Anoxic Interfaces

Cited by 62 publications

References 47 publications

Taphonomic experiments resolve controls on the preservation of melanosomes and keratinous tissues in feathers

Taphonomic experiments resolve controls on the preservation of melanosomes and keratinous tissues in feathers

Organo-mineral interactions and soil carbon mineralizability with variable saturation cycle frequency

Comment on bg-2020-466

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